Combined radio and phonograph system



y 1945- J. w. WHITE ETAL 2,379,617

COMBINED RAD-IO AND PHONQGR[KPH SYSTEM Filed Jul 24, 1942 POWER I /27RADIO SUPPLY RECEIVER AMPLIFIER OUTPUT g 7 32 D E s PHONOGRAPH i PICKUPVVVV III

INVENTORS JULES W WHITE 'ATTQRNEY A Patented July 3, 1945 oomnman mnroAND rnonocmrn SYSTEM Jules W. White and Louis A. G. ter Veen, Marion,-Ind., assignors to Farnsworth Television and ltadio Corporation, acorporation of Delaware Application July 24, 1942, Serial No; 452,226 6Claims. (Ci. 179-10011) This inventionrelates generally to combinedradio receivers and phonographs and more particularly to a switchingcircuit for connecting either a radio receiver or a phonograph pickupdevice to a sound reproducing loud speaker.

Combined radio receivers and phonographs are customarily provided with anumber of circuit components consisting of a radio-frequency amplifyingcircuit and an audio-frequency amplifying circuit, a. phonograph pickup,a power supply and a sound reproducing loud speaker. There is alsoprovided a switching means for connecting either the radio-frequencyamplifier or the phonograph pickup to the audio-frequency amplifierthereby providing a means for selecting either a radio program or aprogram recorded on a recording medium. Previous radio-phonographcombinations do notprovide the high quality re-v production of recordedspeech and music corresponding tothe present high quality of recording,for the reason that interference and-back ground noise signals which arenormally received in a radio receiver make it imperative that the volumelevel and volume range of the audio-frequency amplifier be limited toprevent undue ampliflcation of such interference and background noisesignals. By so limiting the volume range and level in the audiofrequency amplifier, it is impossible to provide the greater undistortedoutput which is needed for reproducing a recorded program.

In previous radio-phonograph combinations, no provision has been madeforcutting oil the flow of power to the radio frequency portion of thecombination during record playing time. Therefore, the life of thisportion of the combination is considerably lessened, as a portion of itsenergized time is wasted while the phonograph is being utilized.Furthermore, there is always an unnecessary drain on the power supplyduring the use oi the phonograph which reduces the power available tothe audio-frequency circuit to thereby reduce the available volume rangeand level which is needed during the use of the phonograph. v

i The principal object of this invention is to improve, in aradio-phonograph combination, the quality of reproduction of recordedprograms.

in a radio-phonograph combination, increased volume range and levelduring reproduction of recorded programs.

Still another object of this invention is to prov vide,-in aradio-phonograph combination, means for providing a greater undistortedoutput during the reproduction of recorded programs than is possibleduring the reception of radio programs. A further object of thisinvention is to increase the life of the radio receiver in aradio-phonograph combination.

A still further object of this invention is to provide, in aradio-phonograph combination, a means I for increasing the amount ofpower availableto Another object of this invention 'is'to provide.

the audio-frequency amplifier during the reproduction of recordedprograms,

In accordance with the present invention there is provided a.radio-phonograph combination consisting of a radio-receiver, aphonograph pickup, an audio-frequency amplifier, a sound reproducingloud speaker and a. power supply for the combination. There is alsoprovided'a switching device and circuits whereby either the radioreceiver or the phonograph pickup may be connected to theaudio-frequency amplifier. Switching means is also provided forconnecting the power supply to the radio receiver only when it isconnected to the audio-frequency amplifier and disconnecting the powersupply from the radio receiver when the phonograph is in use. A switchis also provided for changing the bias in one stage of theaudio-frequency amplifier to increase its volume range and level duringuse of the phonograph. The power supply may thus be disconnected fromthe radio receiver and the amplifier circuit altered in such a way thatit will draw more power to thereby have increased volume range and levelduring periods in which recorded programs are reproduced. v

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims. a

In the accompanying drawing: Fig. 1 is a circuit diagram of a combinedradio and phonograph together with the novel switching circuit providedby this invention. Fig. 2 illustrates the switching circuit-shown inFig. l but in a different operating phase.

Referring now more particularly to Fig. l of the drawing, the combinedradio receiver and phonograph lliustrated therein comprise a radioreceiver I, a phonograph pickup device 2, audio-frequency amplifier 3, asound reproducing loud speaker 4 a power supply 5 and a switch 6. Theradio-frequency amplifier output of radio receiver I is connected toswitch 6 by means of conductor 1, and in switch 6 there is provided -aswitch contact 8 in electrical connection :with the ductive contactsadapted to connect either the radio receiver I or pickup 2 to inputconductor ll conductor I. Another contact id of switch 6 is connected tothe first amplifier tube l2 of amplifier 3. Phonograph pickup 2 isconnected to switch contact I3 by conductor 14. Switch 8 includes arotor having arcuate electrically con- H, is and i3, contact thephonograph of amplifier 3.

There is provided for connecting the power supply 5 to the radioreceiver I, conductor 2|, switching contacts 22 and 23, and conductorwhich is in turn connected to the radio receiver for energizing thevacuum tube circuits therein. Power supply 5 is also connected toamplifier 3 by means of conductors 21 and 28, together with plateresistor '30. Conductor 2! also energizes the anode of amplifier tube Itthrough the coil 32 of loud speaker 4. V

The volume range and level of amplifier 3 is altered by means of a shuntresistor 34 which is grounded and connected through conductor 36,contacts I9, 33 and 39 and conductor 40 across the resistor 4| in thecathode circuit of tube I6. There is provided the usual biasingresistors 43, 44 and 45 for properly energizing tubes l2 and ii ofamplifier When the combined radio receiver and phonograph is operated toreproduce recorded programs, switch 6 is rotated into the positionillustrated in Fig. 1. Phoncgraph pickup 2 is thus connected to theinput of amplifier 3 through conductor l4, contacts l3, l8 and Ill andconductor ll. At the same time resistor 34 is connected in shunt toresistor 4| through conductor 36, contacts 38, I9 and 39 and conductor40. Since contacts 8 and 22 are open when switch 6 is in this position,there is no circuit between power supply 5 and receiver l and there isalso no circuit between the amplifier output of receiver l and the inputof amplifier 3. Therefore, the tubes of radio receiver I receive noenergy since there can be no reproduction of radio programs at this timeand the entire power output of power supply 5 is impressed on theaudioamplifier 3. In addition, resistor 34 is connected across resistor4] which increases the voltage on the cathode circuit of tube [6,thereby changing the class of operation of amplifier 3 and increasingits output to provide greater volume range and level.

Radio programs are reproduced by rotating the switch 3 in a clockwisedirection to the position illustrated in Fig. 2 of the drawing, therebyelectrically connecting contacts 22 and 23 and also contacts 8 and I0.Power supply 5 is thereby connected to the radio receiver I throughconductors 2| and 25 and contacts I1, 22 and 23. The amplifier output ofradio receiver l is connected to amplifier 3 through conductor 1,contacts 3, I0 and I3 and conductor H. The phonograph pickup isdisconnected from amplifier 3 at contact [3 and the shunt includingresistor 34 is also open at contacts 33 and 39. Power having beenapplied to radio receiver I, its output is amplified in audio-frequencyamplifier 3 and reproduced in loud speaker 4. Inasmuch as the powersupply to the amplifier 3 has been reduced, the volume range and levelis reduced to such a value that there cannot be undue distortionresulting from interference and background noises which may be receivedby radio receiver I.

I8 being nents of the radio-phonograph combination, it will be obviousto those skilled in the art that any type of switch arrangementmay beutilized for connecting and disconnecting the illustrated circuits. Itis not intended that this invention shall be limited to thespecificaudio-frequency amplifier circuit illustrated in the drawing norshall the invention be limited to the specific type of phonograph pickupand sound reproducing loud speaker.

F While there has been described what is at present considered thepreferred embodiment of the invention, it will'be obvious tothoseskilled in the art that various changes and modifications may be madetherein the invention, and it is, therefore, aimed in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. In combination, a first signal channel, a second signal channel,amplifier means for amplifying signals from either of said channels, asource of power connected to said amplifier means switch means forconnecting said power source and said amplifier means to said firstsignal channel or said second signal channel to said amplifier, andmeans controlled by said switch for changing the output level of saidamplifier means.

2. In combination, a first signal channel comprising an amplifier, asecond signal channel, amplifier means for amplifying signals fromeither of said channels, a source of power connected to said amplifiermeans, and switch means for simultaneously connecting said source tosaid first channel amplifier and said amplifier means to said firstsignal channel or for simultaneously disconnecting said power sourcefrom said first channel amplifier and connecting said second signalchannel 'to said amplifier means.

3. In combination, a radio channel, a phono graph pickup device,amplifier means for amplitying signals from said channel or said pickupdevice, a source of power connected to said amplifier means, androtatable switch means includin a first group of contacts connected tosaid power source and said radio channel, a second group of contactsincluding a first contact connected to said amplifier means, a secondcontact connected to said radio channel and a third contact connected tosaid pickup device and a rotor including conductive portions adjacenteach group of said contacts in such angular relation to one another thatin one position of said rotor said first group of contacts connect thepower source to said radio channel and the first and second contacts ofsaid second group of contacts connect said radio channel and saidamplifier means whereas in another position of said rotor said firstgroup of contacts are opened to impress the full power output of saidsource of power on said amplifier means and the second and thirdcontacts of said second group of contacts connect said phonograph pickupand said amplifier means.

4. In combination, a radio channel, a phonegraph pickup device,amplifier means for ampli tying signals from said channel or said pickupdevice including in one stage thereof a permanently connected biasingresistor and a second biasing resistor adapted to be connected in shunttherewith, and rotatable switch means including a first group ofcontacts connected to said permaular type of switch ha been disclosedfor connecting and disconnecting the various componently connectedbiasing resistor and said second biasing resistor, and a second group ofcontacts including a first contact connected to said without departingfrom amplifier means, a second contact connected to said radio channeland a third contact connected to said pickup device and a rotorincluding con- .ductive portions adjacent each groupof saidconpermanently connected biasing resistor to increase the volume rangeand level of said amplifier means, and the second and third contacts ofsaid second group of contacts are closed to connect said phonographpickup and said amplifier means.

5. In combination, a radio channel, a phonograph pickup device,amplifier means for amplifying signals from said channel or said pickupdevice includin in one stage thereof a permanently connected biasingresistor and a second biasing resistor adapted to be connected in shunttherewith, a sourc of power connected to said amplifier means, androtatable "switch means including a first group of contacts connected tosaid power source and said radio channel, a second group of contactsconnected to said permanently connected biasing resistor and said secondbiasing resistor, a third group of contacts including a first contactconnected to said amplifier means, a second contact connected to saidradio channel and a third contact connected to said pickup device and arotor including conductive portions adjacent each group of said contactsin such angular relation to one another that, in one position of saidrotor said first group of contacts are closed to connect said powersource to said radio channel, said second group of contacts are open,and the first and second contacts of said third group of contacts areclosed to connect said radio channel and said amplifier means whereas inanother position of said rotor, said first group of contacts are opened,said second group of contacts are closed to connect said second biasingresistor in shunt with said permanently connected biasing resistor toincrease the volume range and level of said amplifier means, and thesecond and third contacts of said third group of contacts are closed toconnect said phonograph pickup and said amplifier means.

6. In combination, a first signal channel comprising an amplifier, asecond signal channel. amplifier means for amplifying signals fromeither of said channels, said amplifier means including a biasing means,energizing means connected to said amplifier means, first switch meansfor simultaneously connecting said energizing means to said firstchannel amplifier and said amplifier means to said first signal channelor for simul taneously disconnecting said energizing means from saidfirst channel amplifier and connecting said second signal channel tosaid amplifier means and means operative simultaneously with said firstswitch means for adjusting said biasing means when. said first switchmeans is operated.

' JULES w. WHITE.

LOUIS A. G. TER VEEN;

